Leading shares suffered their worst monthly fall for more than a year in June, wiping £94bn off the value of Britain's top 100 companies, while the price of gold recorded its biggest quarterly decline for 45 years, on continuing concerns the US Federal Reserve may wind down its huge stimulus package for the American economy this year.

Worries about a credit crunch in China added to the volatility after the country's central bank acted to curb speculative lending during the week, while a scandal over Anglo Irish bank traders joking about its €30bn (£25bn) bailout and talk of derivatives losses in Italy reminded investors the eurozone crisis was far from over.

The FTSE 100 closed at 6215.47 on Friday, down 27.93 points on the day and 5.6% since the start of June. That marked its biggest monthly percentage loss since May 2012.

So a volatile quarter which saw the index come within 90 points of its all time high at 6840 ended with a 3% decline, its worst three month drop since this time last year. Even so, it has still recorded a 4.5% rise so far this year.

The shine has rapidly come off gold since it hit highs of $1,895 an ounce in 2011, buoyed by its status as a safe haven for investors. Gold is used by investors as a hedging bet against rising inflation, but fears of a reduction in quantitative easing are damping concerns about higher prices because less central bank cash will ultimately flow into financial institutions. The strengthening dollar also makes the metal more expensive for non-US currency investors. Chinese traders have stopped buying gold, while demand in India has also been muted.

"Everything that had been driving gold up has gone into reverse," said Julian Jessop, chief economist at Capital Economics. "Gold's own status as a safe haven has been undermined by the recent weakness and volatility in prices, at the same time as the markets are regaining confidence in the US dollar."

The recent rout has hit not just equities and precious metals, but also base commodities, bonds, oil and most currencies apart from the dollar. US bond investors are set for their worst quarterly performance since 1994.

The initial catalyst for the turmoil came on 22 May – just at the FTSE 100 hit a near 13 year peak – when US Federal Reserve chairman Ben Bernanke first signalled he might start reining in the bank's $85bn (£56bn) a month bond buying programme, and accelerated when he repeated the comments just over a week ago. Markets had been strongly supported by central bank actions to stimulate the global economy and took fright at the idea the money taps could be switched off.

Over the past few days a number of Federal Reserve members tried to suggest the reaction to Bernanke's comments had been exaggerated, helping to stem some of the decline. But with mixed economic data from America on Friday, investors were looking ahead nervously to the US non-farm payroll figures next week for further clues to the Fed's thinking.

The People's Bank of China – which sparked talk of a credit crunch in the country by letting short term borrowing costs jump to record highs to discourage banks from reckless lending – also weighed in to calm markets. After soothing if gnomic comments from officials earlier in the week that they would act if necessary, the central bank's governor Zhou Xiaochuan said on Friday: "We will use all kinds of tools and methods to appropriately adjust liquidity and to maintain the overall stability of markets."

Gold prices at the end of June 2013 Photograph: Guardian/Thomson Reuters

The plunge in gold prices has taken analysts by surprise. Judging where gold would sink to was "like catching a falling knife", said Jessop. "Now is perhaps not the best time to try to call the bottom in the price of gold. Nonetheless, it seems premature to write gold off completely."

Capital Economics is predicting gold will be at $1,320 an ounce by the end of the year, down from an earlier forecast of $1,700, while Goldman Sachs recently predicted that gold prices would fall to around $1,050 by the end of 2014.